Diversity and distribution of Finnish aphyllophoroid and heterobasidioid fungi (Basidiomycota): An update

Biogeographical and ecological knowledge of aphyllophoroid fungi has increased substantially after the publication of the Finnish aphyllophoroid checklist. In this paper, we describe the occurrence and distributions of both aphyllophoroid and heterobasidioid fungi in Finland. We introduce 13 species new to Finland: Hyphoderma lapponicum, Mycostilla vermiformis, Proterochaete adusta, Pseudotomentella alobata, Pseudoxenasma verrucisporum, Sistotrema subtrigonospermum, Spiculogloea minuta, Tomentella botryoides, Tomentella neobourdotii, Tomentella subtestacea, Tomentella subpilosa, Tulasnella anguifera, and Tulasnella interrogans. Proterochaete and Pseudoxenasma are new genera to Finland. We also present the record of Caudicicola gracilis for only the second time globally. Furthermore, we present 115 new records (locations) of 53 rare or seldom collected species. In addition, we report 96 species considered new to a specific subzone of the boreal forest vegetation zone in Finland. The records contain notes on the substrata, and the ecology and distribution of nationally new species and are briefly discussed.


Introduction
The checklist of Finnish aphyllophoroid fungi was published in 2009 ). Since that time, substantial new information on both aphyllophoroid and heterobasidioid species has accumulated, which includes a total of 102 species new to Finland (H. Kotiranta, unpublished), 406 records of rare species, and 525 species new to some region (e.g., Kunttu et al. 2016Kunttu et al. , 2018Kunttu et al. , 2019. The species that are new to Finland can be either factually new finds or results of better understanding of species identity due to taxonomic revisions. This accumulated knowledge is mainly explained by recent extensive field inventories and studies, while areas (e.g., Kainuu province, Oulu region) and substrata (e.g., fine woody debris) that had previously received little attention have also been newly surveyed (e.g., Juutilainen 2016).
In the current paper, we present new records of aphyllophoroid and heterobasidioid fungi in Finland, where we consider three types of records: 1) species new to Finland, 2) rare or seldom collected species with a maximum of 10 previous records in Finland, and 3) species that are new to a specific subzone (section) of the boreal vegetation zone in Finland.
We considered both aphyllophoroid and heterobasidioid fungi in their broader sense, approximately following Hansen and Knudsen (1997), with the exception that the gastromycetoid genera were excluded. Although we concentrated mainly on corticioid fungi, the heterobasidioid genera (such as Helicogloea, Spiculogloea, and Tulasnella) were also included, since they were also included in the Finnish checklist of aphyllophoroid fungi ).

Material and methods
Most of the records in this paper were derived by mycologists from field trips and species inventories (e.g., Finnish Atlas of Fungi), but some old herbarium specimens were also studied. A common inventory method was an opportunistic search/sampling for species, which entailed a careful walk through a study site to collect visible sporocarps, and emphasis was placed on sampling multiple habitats and substrate qualities to collect a large number of species and to obtain a representative picture of the species composition of the study site (Stokland & Sippola 2004). Field work by the author PV during 2020 in Lapland was conducted in the form of systematic inventory of sample plots. The work was part of a Natural Resources Institute Finland LUKE led project. The majority of the records date from 2019 and 2020, but some older records were also included.
At the beginning of each fungal record, we provide the biogeographical provinces according to Knudsen and Vesterholt (2008), and Latin province names are presented on the website of FinBIF (2021a) alongside this provincial division. For each record, we named the sites at two or three levels: a municipality and a village, or a topographical site or nature conservation area. If the biogeographical province was the same as in the previous record for the same fungal species, it was not repeated. The Finnish National Uniform Coordinate System (UCS, 27°E; Heikinheimo & Raatikainen 1981) was used to present the coordinates. The forest vegetation subzones ( Fig. 1) follow Ahti et al. (1968), and are also available on the online FinBIF map (FinBIF 2021b). Following the abovementioned sources, the names of the subzones were presented in English (e.g., Ostrobothnia), in contrast to the Latin names that were used for the biogeographical provinces (e.g., Ostrobottnia).
Taxonomy and nomenclature mainly follow  and Hjortstam and Ryvarden (2009), but Bernicchia and Gorjón (2010) was also used for some species, as was Spirin et al. (2019a) for genus Protomerulius, and Svantesson et al. (2019) for the Pseudotomentella tristis group. The Finnish Red List assessment of species according to the IUCN-standard corresponds to Kotiranta et al. (2019). If a species status was determined to be of least concern, it was not mentioned.
The decay stage classification (1-5) of dead wood was carried out according to Renvall (1995), with stage 1 referring to hard dead wood and stage 5 referring to completely decayed wood. This is widely used method for all tree species in the boreal forests (e.g., Korhonen 2009; Siitonen et al. 2009). The diameter of dead wood was measured at chest height if the trunk was complete and from the middle if it was broken. Here, we use the Finnish term 'kelo' to refer to dead and old-growth trunks of Scots pine (Pinus sylvestris) with a silvery-grey, decorticated appearance. Kelo trees are special substrata for fungi due to their extremely slow decay rate (even hundreds of years), long-lasting hard surface and chemical compounds (Leikola 1969;Niemelä et al. 2002;Venugopal et al. 2016). Classification of habitat types follows, to a large extent, the Red List assessment of habitat types in Finland (Kontula & Raunio 2018).
The material were collected, identified, and confirmed by several mycologists as described in the record details, using the following abbreviations: TH = Teppo Helo, JJ = Jari Julkunen, HK = Heikki Kotiranta, MK = Matti Kulju, OM = Otto Miettinen, AM = Aki Moilanen, JP = Jorma Pennanen, and PV = Pyry Veteli. Unless otherwise stated, the collector was also the identifier. The code after the name of the collector represents the personal sampling number of the specimen. Voucher specimens were deposited in the herbaria of the universities of Helsinki (H), Oulu (OULU), Turku (TUR), Jyväskylä (JYV) and Kuopio Natural History Museum (KUO).

Athelia acrospora Jülich
Distribution. New to 3c (Fig. 1). . We are aware that there is also an older unpublished museum specimen (KUO) which was collected on the border of zones 3a and 3b. Because that specimen lacks   exact coordinates, we decided to publish our more accurate JJ 1101 record.

Crustoderma longicystidiatum (Litsch.) Nakasone
Notes. 2 nd -3 rd records in Finland; previous records: Miehikkälä (2a) ). The specimens are conspecific according to ITS-sequences. Notably, both specimens are from coniferous substrate exposed to prolonged cool and humid or wet conditions which may have been the case with the Miehikkälä-collection as well (the habitat was timber sawmill located near rapids). Whether the same holds for the species type, warrants a more thorough taxonomic treatment in the future. Critically Endangered.  Hjortstam (Fig. 14) Distribution. New to 3b (Fig. 1). Distribution. New to 3c (Fig. 1).

Species new to Finland
Hyphoderma lapponicum has been reported from Sweden, Norway, Spain, and one in unpublished (H. Kotiranta) record from Russian Far East (Eriksson & Ryvarden 1975;GBIF Secretariat 2019). The ecology of the species seems to be poorly known, and its delimitation against H. obtusiforme deserves further study.   Mycostilla vermiformis is distributed in temperate and boreal forests of Europe, and it has been found in Sweden, Norway, Denmark, Russia, Poland, Czech Republic, United Kingdom, and France (see Spirin et al. 2019b). The hosts described by Spirin et al. (2019b) were Picea abies and Pinus sylvestris. In Finland, basidiomata grew on coarse trunks of intermediately decayed Picea abies. The site in Helsinki is now partly destroyed. Previous reports of Stypella vermiformis in Finland represent another species. For the taxonomy of the complex see Spirin et al. (2019b).
In the USA, P. adusta grew on a decorticated Populus trichocarpa trunk (Burt 1915), in Canada on Populus trichocarpa and Acer negundo (Martin 1953;Alvarenga et al. 2019), in Russia on an undescribed deciduous tree and a Betula pseudosieboldianum (Wells & Raitviir 1966;Alvarenga et al. 2019), in Norway on an undescribed hardwood (Alvarenga et al. 2019), in Germany on fallen Populus trunks (five records), inside a rotten Populus stump (one record), and on a fallen Quercus trunk (one record) (Rödel et al. 2020), and in Finland on the bark of a fallen and hollow Populus tremula trunk (2017 record). There is no description of the substrate in the 1964 Finnish record. In summary, P. adusta seems to demand, or at least to prefer, deciduous trees, especially Populus as its substrate (Rödel et al. 2020).
With the exception of substrate, the ecology of P. adusta remains unrecorded. Rödel et al. (2020) report that one of their specimens grew on an eastern bank of a river. The 2017 Finnish record grew on a very old Picea abies dominated thin-peated Vaccinium myrtillus -Vaccinium vitis-idaea spruce mire with a substantial amount of dead wood. Populus tremula and Salix caprea were secondary species in the forest. There is no description of the ecology in the 1964 Finnish record.
The fresh basidioma from the 2017 Finnish record was smooth -finely tuberculate, very thin and almost transparent. A cross section of the dry basidioma was a minimum of 20-40 µm compared to the cross sections 100-300 µm (Alvarenga et al. 2019) or 110-220 µm (Rödel et al. 2020). The dry basidioma of the 1964 Finnish record is rather finely grandinoid -finely tuberculate.
Pseudotomentella alobata has been reported in Sweden, Norway and Slovenia (Svantesson et al. 2019). To date, data on habitat are scarce, but recent Scandinavian collections have been made in old-growth coniferous or mixed forests on soil with high pH (Svantesson et al. 2019). The species is described from the Pseudotomentella tristis group. Most of the P. tristis specimens in the collections are incorrectly identified, so the distribution of the species is not reliably known. It is probably quite rare.
According to GBIF Secretariat (2019), Pseudoxenasma verrucisporum is known in Sweden, Norway and Austria. Eriksson et al. (1981) report that this species typically inhabits conifer branches in closed, moist forests, often growing together with Globulicium hiemale, as in the case of the Finnish collection. In a Nordic context, the species appears to be southern (most finds are from the hemiboreal zone), although it may extend further north along the seacoast. The species has not been found in Russia, which would indicate that it may have an oceanic distribution (V. Spirin, pers. comm.). Most collections have been made close to the coast, where it can be locally common. Overall, the species appears to be rather rare. The collection from Helsinki fits well with this general pattern, as it was found in an old, closed spruce forest on the southern coast of Finland.
Sistotrema subtrigonospermum is a globally distributed species: records have been reported in several countries in Europe, Africa, North and South America, India, and Polynesia (see Martini 2021a (Roberts 1997;Trichies 2002;Rödel 2014;Spirin 2016;Spirin 2019b). The Finnish specimen was collected in association with Tulasnella allantospora on a decayed Picea abies trunk.
Tomentella botryoides is a widely distributed species that has been found in many countries in Europe, as well as in Morocco, Caucasus, Russian Far East, India and North America (see Martini 2021b). The collections have been made both from deciduous (e.g., genera Quercus, Fagus, Betula) and coniferous trees (e.g., genera Thuja, Abies, Pinus, Pseudostuga), where the substrate were mainly intermediately or strongly decayed lying trunks and branches (see Martini 2021b).
Tomentella subtestacea has a global distribution and GBIF Secretariat (2019) has listed it in Sweden, Norway, Denmark, Estonia, Russian Federation, Belarus, Ukraine, Germany, Poland, Belgium, France, Czech Republic, Hungary, United Kingdom, Spain, Azerbaijan, USA, Mexico and Laos. Ecological requirements are unknown or unreported. Previously Tomentella aff. subtestacea was reported in Finland in 1979 ), although the identity of the specimen remained unclear.
Tulasnella anguifera has previously been reported only in France and United Kingdom (Roberts 1992;GBIF Secretariat 2019;Trichies 2002) and was collected from decayed trunks or branches of Picea abies, Picea sp., and Prunus spinosa (Roberts 1992;Trichies 2002). Both Finnish specimens grew inside basidiomata of Athelia bombacina on decorticated Pinus sylvestris kelo trees. The second specimen occurred on the same trunk, in association with Sistotremastrum suecicum, Tulasnella permacra, and Tulasnella albida.
Tulasnella interrogans has been reported in Belgium, France, United Kingdom, and Spain (Roberts 1992;Dämon 2001; GBIF Secretariat 2019), where it was collected from decayed trunks or branches of Corylus sp., Picea sp., Salix sp. and inside a basidioma of Botryobasidium subcoronatum (Roberts 1992;Trichies 2002). A Finnish specimen grew under and around basidioma of Athelia bombacina on a decorticated kelo branch of Pinus sylvestris. The habitat had been thinned at some point, but substantial amounts of decaying pine wood were still present onsite from the previous tree generations.
Tulasnella is a genus whose species' ecology, biogeography, substrata and habitat requirements are poorly known. Notes on habitats in old collections are often incompletely described and hence do not allow conclusions to be drawn. Many of the Tulanella species appear to favor herb-rich forests, but some occur in very diverse biotopes and can even be found in barren places. It is possible that some Tulasnella species even prefer old-growth forests. In fact, our specimens of these two Tulasnella species were found in one of the finest natural forests in Finland. Nonetheless, the number of collections is still insufficient to draw conclusions about the ecological requirements of these species.
The red-list status of the species new to Finland has not been assessed.

Species with only one previous global record
The second global record of Caudicicola gracilis was found in Oulu, Finland. The basidioma grew on a sawn block of Betula sp. that was leaning against a tree in a rather moist spruce-dominated drained and transformed mire. The first recording of C. gracilis was in 2014-2015 in Pyhäjärvi, central Finland and was described as a new species (Kotiranta et al. 2017). The habitat was a boreal wooded, drained minerotrophic mire. Spruce was the dominant tree species intermixed with pine, birch and some willow. All the basidiomata grew on the undersides of spruce or pine stumps (roots) and could only be seen after the stumps had been lifted from the ground (Kotiranta et al. 2017). However, if this is the typical growth habit of this species, then it will be a difficult species to detect. Caudicicola gracilis appears to be a wood-or litter-decomposer, since there are no mycorrhizal species in Steccherinaceae or in Polyporales (Hibbett et al. 2014).

Significant extensions of the known distribution range
Most of the new records were found in expected regions, relatively close to their previously known distribution. Nonetheless, the records of some species were located far from their earlier finds or were found in an unexpected location. This 'expansion' of the species' distribution range can be largely explained by the increasing survey activity in different parts of Finland. The new record of Trechispora stellulata in Enontekiö is 570 km north from the nearest previous record in Puolanka. The new record of Ceriporia bresadolae in Helsinki extends its known range by 500 km to the south. However, it should be noted that collections identified as C. bresadolae in Estonia (Runnel et al. 2021), are actually closer than the previous collections in Finland (NATARC 2019). Similarly, the new records of Protodontia subgelatinosa in Enontekiö, Amaurodon cyaneus, Protomerulius brachysporus and Tomentella fuscocinerea, all in Kuhmo, were found approximately 500 km further north compared to previous records. Tomentellopsis zygodesmoides was found in Sotkamo, which is situated 400 km north of the nearest previously known location in Tuusula.

Conclusions
The occurrence and distribution of many aphyllophoroid fungal species are still poorly known in Finland, as demonstrated by this article. Our new records indicate that many species most likely do not have such a scattered distribution as suggested by previous records. Thus, there are still large gaps in our knowledge of their ecology, biogeography, substrata and habitat requirements. The reasons behind this include time-consuming sampling, small basidiomata that are difficult to find, narrow ecological niches (substratum), changing taxonomy, and challenges in species identification. For example, the fungal communities that occupy the smallest fractions of woody debris seem to be poorly known, since this substrate has been commonly overlooked. However, new records are reported frequently and, therefore, knowledge accumulates all the time. New information on aphyllophoroid fungi will be gathered when performing field surveys in poorly studied areas and neglected habitats, or on species with tiny basidiomata. More effort should be allocated into field studies to establish which species are truly rare and to determine the actual distribution range. Naturally, a certain portion of aphyllophoroid fungal species are truly rare or geographically restricted, for example, due to habitat specialization. All such additional knowledge of species occurrence and habitats is important for a deeper understanding of diversity, ecology and conservation requirements of aphyllophoroid fungi.